An image display apparatus such as a projector has been widely used from the past. For example, light from a light source is modulated by a light modulation element such as a liquid crystal element, and the modulated light is projected on a screen or the like, thus displaying an image. For example, Patent Document 1 describes a projector including a light source apparatus. The light source apparatus is formed of a lamp, such as a halogen lamp, and a reflector that reflects light of the lamp. Patent Document 1 describes a technology for suppressing a decrease in reliability due to the rise of the internal temperature of the projector (paragraph [0056] etc. of Patent Document 1).
Recently, products that adopts solid-state light sources, such as an LED (light-emitting diode) and an LD (laser diode), as light sources used in projectors, have been increasingly used instead of mercury lamps, xenon lamps, and the like used in related art. The fixed light sources such as LEDs have advantages such as having long lifetime, no replacement of lamps, which is necessary in related art, and lighting-up immediately after power-on.
For example, Patent Document 2 describes a projector in which a solid-state light source is used as an excitation light source. Blue laser light that is output from the solid-state light source is applied to a phosphor wheel as excitation light. The phosphor wheel includes a base and a phosphor layer formed thereon. Excitation light is applied to the phosphor layer, and thus yellow fluorescence is emitted. The blue light and yellow light emitted from the phosphor layer are combined, to output white light (paragraphs [0028], [0029], etc. of Patent Document 2).
Patent Document 2 describes heat generation of the phosphor wheel due to the application of the laser light. For example, when the application amount to the phosphor wheel is increased so as to improve the output of the light source apparatus, the amount of heat generation from the phosphor wheel is also increased. In Patent Document 1, cooling of the phosphor wheel is achieved by applying the excitation light to a predetermined position while rotating the phosphor wheel. Further, cooling performance is improved by using crystalline members excellent in thermal conductivity, such as crystal and sapphire, for the base material of the phosphor wheel (paragraphs [0005], [0006], etc. of Patent Document 2).
Patent Document 1: Japanese Patent Application Laid-open No. 2012-215750
Patent Document 2: Japanese Patent Application Laid-open No. 2012-173593